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A LIGHT-SENSITIVE pigment derived from vitamin B2 may help to set
the body’s clock.

Scientists reported earlier this year that bright light on the back of the
knees can reset the body’s daily rhythms(This Week, 24 January, p 11). Now
Yasuhide Miyamoto and Aziz Sancar at the University of North Carolina in Chapel
Hill have shown that cryptochrome, a derivative of vitamin B2, may be
the light-sensitive molecule involved in this response.

The researchers found the pigment in neurons which connect to the
suprachiasmatic nucleus, a brain region containing the “master clock” (
Proceedings of the National Academy of Sciences, vol 95, p 6097). It is a
different pigment from that involved in vision, which may explain why blind
people who lack vision proteins are able to maintain a normal daily rhythm.

THE discovery in Eritrea of a human skull around one million years old has
filled a gap in the fossil record of humans in Africa, between 1.4 million and
0.6 million years ago. The skull, described by an international research team in
this week’s issue of Nature (vol 393, p 458), shows an intriguing mix
of ancient (Homo erectus/ ergaster) and modern (Homo
sapiens) features.

If the age of the skull is confirmed, it would show that H. sapiens
-like features appeared around 300 000 years earlier than was thought. The
anatomy of the skull is different from that of humans living in southern Asia a
million years ago. The find confirms that anatomy was very variable at that
time, although it is uncertain whether the skull will clarify where and when the
first humans arose.

TIME is running out for the West Antarctic ice sheet, a NASA scientist says.
At a meeting of the American Geophysical Union in Boston last week, he predicted
that the ice sheet would be gone in between 1000 and 5000 years.

“In the past 11 000 years, it’s lost two-thirds of its mass,” says Robert
Bindschadler of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Bindschadler extrapolated from changes since the West Antarctic ice started
shrinking about 11 000 years ago.

The melting sheet could help to resolve a puzzle—why sea level is
rising by two millimetres every year when known sources account for only half
that. Bindschadler says West Antarctica may add the extra millimetre.

Gabrielle Boulianne of the University of Toronto and her colleagues report
that they have increased the lifespan of fruit flies by 40 per cent by making
them produce the human enzyme superoxide dismutase or SOD in their motor neurons
(Nature Genetics, vol 19, p 171). SOD inactivates oxygen radicals,
byproducts of metabolism long suspected to cause the cellular damage that leads
to ageing.

The results suggest that motor neurons are a weak link in the fly’s defence
against free radicals—and the same may be true for humans. Boulianne says
SOD is widespread in animals. “Now we know that it can have a profound effect on
longevity by acting in only a few cells,” says Boulianne. “We’d like to look for
that effect in other organisms.”

STRANGE domes on the icy surface of Jupiter’s moon Europa suggest that an
ocean may lie not very far below.

Julie Rathbun of Cornell University in Ithaca, New York, says the Galileo
spacecraft spotted the domes, which are each a few kilometres across. They are
thought to form when parcels of slightly warmer ice underneath the surface
slowly rise until they warp the outer layer.

Rathbun told last week’s meeting of the American Geophysical Union in Boston
that this process could only have moulded the domes if Europa’s ice is no more
than a few tens of kilometres thick—leaving ample room for a deep, liquid
ocean below.

Margaret Kivelson of the University of California at Los Angeles says data
gathered by the Galileo spacecraft indicate that Jupiter’s moon Callisto does
not generate its own magnetism. Instead, the field detected is an echo of
Jupiter’s stronger field sweeping through the moon’s interior.

This induced field could only exist if Callisto contains an electrically
conducting layer, Kivelson said at last week’s Boston meeting of the American
Geophysical Union. An ocean 10 kilometres deep with the same conductivity as
seawater fits the bill surprisingly well. Although Callisto’s frozen terrain
lacks any sign of water, models have suggested that internal heat and pressure
could be melting ice 200 kilometres below the surface.